Background Magnesium salts bind dietary phosphorus, but their use in renal patients is limited due to their potential for causing side effects. The aim of this study was to evaluate the efficacy and safety of magnesium carbonate (MgCO 3 ) as a phosphatebinder in hemodialysis patients. Methods Forty-six stable hemodialysis patients were randomly allocated to receive either MgCO 3 (n = 25) or calcium carbonate (CaCO 3 ), (n = 21) for 6 months. The concentration of Mg in the dialysate bath was 0.30 mmol/l in the MgCO 3 group and 0.48 mmol/l in the CaCO 3 group. Results Only two of 25 patients (8%) discontinued ingestion of MgCO 3 due to complications: one (4%) because of persistent diarrhea, and the other (4%) because of recurrent hypermagnesemia. In the MgCO 3 and CaCO 3 groups, respectively, time-averaged (months 1-6) serum concentrations were: phosphate (P), 5.47 vs. 5.29 mg/dl, P = ns; Ca, 9.13 vs. 9.60 mg/dl, P \ 0.001; Ca 9 P product, 50.35 vs. 50.70 (mg/dl) 2 , P = ns; Mg, 2.57 vs. 2.41 mg/dl, P = ns; intact parathyroid hormone (iPTH), 285 vs. 235 pg/ml, P \ 0.01. At month 6, iPTH levels did not differ between groups: 251 vs. 212 pg/ml, P = ns. At month 6 the percentages of patients with serum levels of phosphate, Ca 9 P product and iPTH that fell within the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines were similar in both groups, whereas more patients in the MgCO 3 group (17/23; 73.91%) than in the CaCO 3 group (5/20, 25%) had serum Ca levels that fell within these guidelines, with the difference being significant at P \ 0.01. Conclusion Our study shows that MgCO 3 administered for a period of 6 months is an effective and inexpensive agent to control serum phosphate levels in hemodialysis patients. The administration of MgCO 3 in combination with a low dialysate Mg concentration avoids the risk of severe hypermagnesemia.

In terms of both exogenous sources (diet), and endogenous production (activation through exposure to ultraviolet light), vitamin D is unique. Few foods naturally contain vitamin D and only a few are fortified with vitamin D. Most people get more than 90% of their vitamin D requirements from exposure to sunlight. Those who protect their skin from ultraviolet-B radiation with clothing or sunscreen, the elderly, and dark-skinned individuals have limited capacity to produce vitamin D. Vitamin D deficiency is common in the general population and even more common in patients with chronic renal failure (CKD). Increased use of sun-blocking agents and decreased exposure to sunlight, to reduce the risk of skin cancer, attributed to exposure to UV radiation, may contribute to the increase in vitamin D deficiency in the population. These issues are particularly important in the dialysis population who are at particular risk because these, mostly elderly, individuals have an inactive life style and have reduced exposure to sunshine and UV light, thus limiting the actinic synthesis of vitamin D. The nephrology community seems to have overlooked the importance of vitamin D for overall health and well being in patients with CKD. Recently however, several authors have called attention to the role of plasma 25(OH)D3 levels in mineral metabolism dysregulation in patients with chronic kidney diseases, and those on dialysis. Vitamin D not only contributes to skeletal health but also plays a major role in the health of a wide variety of other organ systems. It seems that vitamin D supplementation is the most effective way of preventing vitamin D deficiency.

Serum Mg is lower and serum PTH higher in patients dialyzed with lower Mg concentration dialysis solution compared to those with higher Mg concentration dialysis solution. Our study confirms previous reports that serum Mg may have a suppressive role on PTH synthesis and/or secretion, and thus may play a role in pathogenesis of adynamic bone disease that often develops in patients on chronic PD with high calcium and high magnesium concentrations.